Spatial light modulators used for imaging applications come in many different forms. Transmissive liquid crystal device (LCD) modulators modulate light by controlling the twist and/or alignment of crystalline materials to block or pass light. Reflective spatial light modulators exploit various physical effects to control the amount of light reflected to the imaging surface. Examples of such reflective modulators include reflective LCDs, and digital micromirror devices (DMD™).
Another example of a spatial light modulator is an interferometric modulator that modulates light by interference, such as the iMoD™. The iMoD employs a cavity having at least one movable or deflectable wall. As the wall, typically comprised at least partly of metal, moves towards a front surface of the cavity, interference occurs that affects the color of light viewed at the front surface. The front surface is typically the surface where the image seen by the viewer appears, as the iMoD is a direct-view device.
Currently, iMoDs are constructed of membranes formed over supports, the supports defining individual mechanical elements that comprise the picture elements (pixels) of an image. In a monochrome display, such as a display that switches between black and white, one iMoD element might correspond to one pixel. In a color display, three iMoD elements may make up each pixel, one each for red, green and blue.
The individual iMoD elements are controlled separately to produce the desired pixel reflectivity. Typically, a voltage is applied to the movable wall of the cavity, causing it be to electrostatically attracted to the front surface that in turn affects the color of the pixel seen by the viewer. Since the iMoD is based upon a membrane, however, some objectionable artifacts may occur around the edges of the elements. As the membrane deflects or deforms towards the front surface, it typically does not achieve a uniform flatness. The portions of the membrane that curve away from the fully-deformed membrane held tightly against the front surface are at differing distances away from the front surface, which may result in the objectionable artifacts.
Since the iMoD typically functions as a direct-view device, the back surface of the movable portion of the cavities may be operated upon without negatively affecting the image quality. This may also provide more freedom in other aspects of the manufacture of these devices.